Newbie -- Button in another window - How to click?

Folks --

First off - my apologies if this is an off topic question ( or Worse -
an FAQ question ). If someone knows of a better place to ask - please
tell me.

I am working on an office systems application, In this application,
originally one had to type in some info on four fields, a bit of
script would run and then the user would be instructed to press one of
the buttons on the neighboring browser window to go on in the
process. I have been directly told that it needs to press the
button, not to clone the code that lives under it.

Would someone be kind enough to tell me how? Long web searches have
yeilded some ideas, but I am worried that none will work in the end
product.

These are Linux workstations as well as windows running Firefox
browsers.


--dan